Flux for use in the treatment of light metal



Patented Nov. 11, .1941

UNITED STATES PATENT OFFICE rL x Fon USE IN THE TREATMENT OF LIGHT METAL Harry Rowland Leech, Salford, and Gordon James Lewis, Eccles, near Manchester, England,

, assignors to Magnesium Elektron Limited, London, England, a British company No Drawing.

Application December 5,1940, Se-

rial No. 368,732. In Great Britain November v2 Claims.

This invention relates to fluxes for use in the melting of light metals consisting of magnesium metal, magnesium base alloys and aluminiummagnesium alloys, all. referred to hereinafter as metal.

As is well known, considerable oxidation of the metal can occur in contact with air when the metal is being melted or is in the molten state. The metal also reacts with the nitrogen in-the air with formation of nitrides.

The losses of metal which are thus caused and the inclusion of reaction products such as oxides and nitrides as impurities in the metal can be minimized by the use of a flux.

Two main kinds of flux hav eheretofore been proposed, viz

(a) A thinly fluid or non-inspissated flux of low melting point such as carnallite (see for example the specification of the applicant companys Patent No. 469,347) which is more parreadily inspissated by the addition to the melt oi inspissating agents or an inspissate'd flux.

6. It should not react chemically with the metal, to give impurities which will have an adverse efiect on the properties of castings made therefrom.

ticularly intended merely for protecting the metal against oxidation, and (b) The use of an inspissated flux which was originally described in the specification of the applicant company's Patent No. 219,287, and is more particularly intended for reflning the meta1 as well as for preventing oxidation.

The object of the present invention is to provide an improved flux oi the thinly fluid type (a) 1. It should have a low melting point. so that it will melt and cover the surface of the metal at the lowest possible temperature and well below the melting point of the metal. v

2. It should have a low surface tension and good wetting properties, so that it will quickly and completely cover the metal surface.

3. It should give a thinly fluid melt. i. e. e: a low viscosity, and therefore should not contain such a proportion of inspissating agents (such as magnesium oxide and calcium fluoride) as will have an appreciable inspissating eflect.

4. It should be a free flowing powder at ordinary temperatures, and of such a degree of fine- The desirable properties of such a flux are;

I Per cent Magnesium chloride 34 Calcium chloride 30 g Sodium chloride 35,

Potassium chloride 'r Magnesium oxide 1 7. It should bestable in use so that, for ex- Per cent Magnesium chloride.- 20-50 Calcium chloride 25-40 Sodium chloride Up to 30 Potassium chloride Up to 30 Magnesium oxide 0- 5 1 Together within the limits 20-25%.

The composition of one flux which has given particularly good results is:

In general, we flnd that the best results are obtained within a range of plus or minus 5% .of each constituent of this composition.

We find that with the use of this flux, the flux consumption is low and losses of metal by oxidation during melting are reduced to very small proportions.

In preparing the flux, we have melted the constituents together and ground them to a ness that it may readily, uniformly and economically be distributed over the metal surface in the powder form.

5. It should be-readily removable from the metal when melting is complete, in order not to be retained as an impurity in the metal when cast, with consequent adverse eflect on the mechanical properties and corrosion resistance. PM this P p e it should be capable of beins powder of suitable flneness or we have mixed the constituent materials and then ground them or we have ground the materials separately and then mixed them. There is no considerable difference' in efllciency discernible between these methods. We normally grind the flux to produce apowder which all passes through a 10 mesh B. S. sieve and not more than 20% passes through a 200 mesh 28. B. sieve.

The flux. according to the present invention can be used in dealing with both virgin metal 1 9.005% chloride ion. In other'tests up to and even over 98% melting efficiency has been obtained. V I From the metal thus prepared, alloys. according to D. T. D. specifications were manufactured and test specimens from these batches showed a corrosion resistance and mechanical properties which were at least as good as such alloys as Per cent 7 Magnesium chloride 34 Calcium chloride 30 ,Sodium and potassium chlorides 35 Magnesium oxide 1 As melting proceeded, more flux of the same composition was added to control burning of the metal; in all kgs. of the fluid flux was used. When melting was complete, heating was continued until vthe contents of the pot had been brought to a temperature of 745 C. whereupon the metal was agitated by plunging with an iron tool. The molten metal was then treated with 7.25 kgshof the flux of the following composition:

Per cent Magnesium chloride 37 Calcium chloride 14 Sodium' and potassium chlorides l5 Magnesium oxide 13 Calcium fluoride 21 This quantity of flux was applied in the following manner:

A portion of the flux was stirred into-the metal by plunging as above and then the remainder was sprinkled uniformly over the surface to form a protective cover and the metal allowed to standand cool to 720 C. whereupon it was poured into 1 ingots. The yield thus obtained was 2,196 kgs. (96.1% melting efliciency) of metal containing heretofore, produced. In producing such alloys, the purified magnesium was remelted and alloyed with the aid of the fluid flux, the melt was then further protected by means of the inspissated flux and the usual superheating and settling processes, where necessary, were carried out in accordance with applicant company's Patents Nos. 359,425 and 336,498.

We claim:

1. A flux for use with metal of the kind hereinbefore defined consisting of at least 95% of the:l following substances in the amounts specie Per cent Magnesium chloride 20-50 Calcium chloride 25-40 Sodium chloride Up to 30 Potassium chloride Up to 30 Magnesium oxide 0-5 the sodium chloride and potassium chloride to-* gether amounting to between 20 and 2. A flux for use with metal of the kind hereinbefore defined having the following composition! Per cent Magnesium chloride 31-37 Calcium chloride 27-33 Sodium chloride 32 38 Potassium chloride Magnesium oxide .05-4

the total of these ingredients amounting a; at 9 least HARRY ROWLAND LEE'Cl-I. GORDON 'JANIES LEWIS. 

